Summary: A new imaging study provides anatomic support for the argument that concussion is unique and distinct from PTSD and depression. In that study of 30 OIF/OEF mTBI services members with co-morbid PTSD and depression examined with high angular resolution diffusion imaging (HARDI), loss of white matter integrity was associated with chronic mild TBI in a widely distributed pattern of major and minor fiber bundles that included the corpus callosum, internal capsule, and superior longitudinal fasciculus. Loss of white matter integrity correlated with duration of loss of consciousness and, most notably, with "feeling dazed or confused." It did not correlate with the diagnosis of PTSD or depressive symptoms. The diffuse loss of white matter integrity appears consistent with systemic mechanisms of damage shared by blast- and impact-related mTBI that involve a cascade of inflammatory and neurochemical event